Implant, implantation device, implantation method

ABSTRACT

An implant suitable for being anchored with the aid of mechanical vibration in an opening provided in bone tissue. The implant is compressible in the direction of a compression axis under local enlargement of a distance between a peripheral implant surface and the compression axis. The implant includes a coupling-in face which serves for coupling a compressing force and the mechanical vibrations into the implant, which coupling-in face is not parallel to the compression axis. The implant also includes a thermoplastic material which, in areas of the local distance enlargement, forms at least a part of the peripheral surface of the implant.

BACKGROUND OF THE INVENTION

The invention lies in the field of medical technology and concernsimplants, surgical devices, and surgical methods. It especially concernsimplants suitable for being anchored in hard tissue, in particular inbone tissue, with the aid of mechanical vibrations, through which a, forexample, thermoplastic material provided on the implant is liquefied inplaces where it is in contact with the hard tissue.

Such implants and corresponding methods for anchoring these in bonetissue are known from the publications WO 02/069 817, WO 2004/017 857and WO 2005/079 696. The thermoplastic material of such implants isliquefied by mechanical vibrations while being pressed against osseousmaterial, so that it is pressed into cavities (pores, artificiallyproduced cavities) of the osseous material. This results in a mosteffective anchoring of the implant in bone tissue.

There are situations however, in which anchoring of implants in hardtissue by mechanical vibrations according to the state-of-the-arttechnology does not suffice or in which, for technical, anatomical orphysiological reasons, it is not possible to load a known implant withsufficient vibratory energy to ensure a reliable anchoring by the knownmethods.

It is therefore the object of the invention to provide implants suitablefor being anchored in bone tissue under conditions, which hitherto madesuch implantations impossible or extremely difficult. It is also theobject of the invention to provide methods of anchoring implants, whichpermit an implantation under conditions, which hitherto made suchimplantations impossible or extremely difficult.

BRIEF SUMMARY OF THE INVENTION

A first aspect of the invention provides an implant suitable for beinganchored in an opening in bone tissue with the aid of mechanicalvibration. The implant is able to be compressed in the direction of achosen compression axis with the effect of a local enlargement of adistance between a peripheral implant surface and the compression axis(measured at right angles to the compression axis). The implantcomprises a coupling-in face for the coupling of a compressing force andof the mechanical vibration into the implant, and a thermoplasticmaterial, which forms at least a part of the implant surface in theregion of the aforementioned distance enlargement.

A corresponding method of implanting such an implant in bone tissuecontains the following steps:

providing an opening in the bone tissue;

positioning the implant in the opening so that the compression axisextends essentially parallel with an opening axis;

coupling a compressing force and mechanical vibrations via thecoupling-in face into the positioned implant, thereby causing theimplant to be compressed and, due to the distance enlargement, to bepressed at least locally against the side walls of the opening andtherewith causing the thermoplastic material to liquefy at least partlywhere it is in contact with the side walls and to be pressed into thestructures of the bone tissue, in order to form a form-fit connectionafter re-solidification.

The methods and implants described in this text are suitable forimplanting an implant in bone tissue, as well as in other hard tissue(especially dentine), and in bone tissue or other hard tissuereplacement material. For reasons of simplicity, the following textmostly mentions bone tissue—meaning preferably live bone tissue, thisincludes the possibility of performing steps of a surgical operation exsitu. However, the teaching of this text also applies to other hardtissues and to hard tissue replacement material.

In the present text the term “implant” is used for describing anartificially produced element, which is brought into the body and eitherremains there permanently, is resorbed there, or is removed after acertain period. On one hand, the term “implant” is used in particularfor elements suitable for connecting two parts of the skeleton, orbetween one part of the skeleton and a soft tissue part, or between atleast one part of the skeleton and another object; this also includesimplants used in dental surgery such as the classic dental implants. Onthe other hand, the term is also used for describing endoprostheses suchas e.g. joint prostheses, bone prostheses, intervertebral discprostheses, artificial ligaments or tendons, artificial teeth,endodontic posts, etc.

In this text “thermoplastic material” is used for describing a materialcomprising at least one thermoplastic component able to be liquefied bymechanical vibrations while in contact with a hard surface. Thefrequency of the mechanical vibrations often lies between 2 kHz and 200kHz and their amplitudes are around 10 μm, i.e. between 1 μm and 100 μm.If the thermoplastic material is to take over a load bearing functionand is to liquefy only in the named contact areas—correspondingembodiments are described below—it ought to have an elasticitycoefficient of more than 0.5 GPa and a plastification temperature of upto 200° C., of between 200° C. and 300° C. or of more than 300° C.Depending on the application, the thermoplastic material may or may notbe resorbable.

Suitable non-resorbable thermoplastic materials are, each of medicalquality, polyolefines (e.g. polyethylene), polyacrylates,polymethacrylates, polycarbonates, polyamides, polyesters,polyurethanes, polysulfones, liquid crystal polymers (LCPs),polyacetals, halogenated polymers, in particular halogenatedpolyolefines, polyphenylene sulphones, polysulfones, polyaryletherketones (e.g. polyether etherketone PEEK), polyethers, or correspondingcopolymers and/or blended polymers and/or composites of such polymers,in particular polyamide 11 or polyamide 12.

Suitable resorbable thermoplastic materials are, each of medicalquality, thermoplastic polymers based on lactic and/or glycolic acid(PLA, PLLA, PGA, PLGA etc.) or polyhydroxy-alkanoates (PHA),polycaprolactones (PCL), polysaccharides, polydioxanons (PD),polyanhydrides, polypeptides, trimethyl-carbonates (TMC), orcorresponding copolymers and/or blended polymers and/or composites ofsuch polymers. Especially suitable as resorbable thermoplastic materialsare poly-LDL-lactides (e.g. available from Böhringer under thecommercial name Resomer LR706) or poly-DL-lactides (e.g. available fromBöhringer under the commercial name Resomer R208).

Returning to the first aspect of the invention, in most embodiments,although not necessarily, the compression causes a local enlargement ofan outer cross-section at right angles to the compression axis. The term“outer cross-section” describes the cross sectional area encompassed byan outer contour of the element cut at right angles to the compressionaxis, i.e. the presence of possible cavities within the implant isdisregarded in the calculation of the outer cross-section. In manycases—although not necessarily—an enlargement of the outer cross-sectionsignifies an enlargement of the cross sectional area encompassed by aconvex envelope (convex hull) of the implant body.

The coupling-in face is advantageously at least partly planar andextends at an angle to the compression axis. “At an angle to thecompression axis” in this context means, “not parallel to thecompression axis”. The coupling-in face being perpendicular to thecompression axis, i.e. at a right angle, is particularly advantageous.An angle between the compression axis and the coupling-in face of atleast 45°, or better still, of at least 60° is generally preferred.

The thermoplastic material makes up at least a part of the implant; itmay form the whole implant. Besides thermoplastics the thermoplasticmaterial can also comprise non-thermoplastic components, such asreinforcing fibers, reinforcing splints, filling materials etc., or itmay also constitute a partial or complete coating of an implant part ofa non-liquefiable material (e.g. titanium) or a material which isliquefiable only at substantially higher temperatures (e.g. PEEK coatedwith PLA). Non-thermoplastic components can be evenly distributed in thethermoplastic material or be present in varying concentrations. Theimplant can further comprise areas free of thermoplastic material. Suchareas may be of metal, glass, ceramic material, or of non-thermoplasticmaterials or thermoplastic materials liquefiable at substantially highertemperatures compared to the basic thermoplastic material.

The selected compression axis is generally a specific axis of theimplant, i.e. the implant is fashioned such that compression along thiscompression axis is clearly defined and controlled and results in thedesired local enlargement of the distance between the peripheral surfaceand the compression axis, i.e. the desired enlargement of the crosssectional area. In particular, the compression effect along thecompression axis at a given (small) compressing force can besubstantially greater than along other axes. Compression along otheraxes, such as perpendicular to the chosen compression axis, in additionor as an alternative will not result in an enlargement of the crosssectional area perpendicular to the chosen axis, cannot be carried outin a controlled manner and/or only with excessive energy unacceptableunder conditions prevalent during surgical operations. In someembodiments, the compression axis may be marked by symmetry, e.g. theimplant may be approximately rotationally symmetrical in relation to thecompression axis.

The term “liquefied” describes a condition of the thermoplastic materialin which it is plastic to the extent that, while under pressure, it canpenetrate pores whose dimensions are smaller by at least one magnitudethan a characteristic dimension of the implant. In this sense,“liquefied” also applies to thermoplastic material when it comprises acomparatively high viscosity of e.g. up to 10⁴ mPa·s.

The invention according to the first aspect treads a new path comparedwith the state-of-the-art technology. The state-of-the-art technology isfamiliar with methods of providing an opening (e.g. bore) in the osseoustissue and subsequently anchoring the—e.g. roughly pin shaped—implant inthe opening by positioning it in the opening and applying ultrasonicvibration to it. During this process, the thermoplastic material of theimplant may be liquefied on the circumferential surfaces of the implantand, if applicable, penetrate pores along the walls of the tissueopening. However, it is found that the anchoring effect of this‘non-pressurized’ penetration into pores is often rather moderate.According to the state-of-the-art technology, it is possible to achievea lateral pressure by shaping the tissue opening conically, which iselaborate. In contrast, according to the invention, pressure in lateraldirection is increased by the compression and accompanying enlargementof the distance between compression axis and peripheral implant surface.This on the one hand increases the friction forces generated on thecircumferential implant surface and causes the energy coupled into theimplant via the mechanical vibrations to induce a liquefaction of thethermoplastic material precisely in that region, i.e. laterally, alongthe circumferential surface. On the other hand, the lateral pressurealso drives the liquefied material into laterally existing pores orother structures (surface structures, cavities etc.) of the tissueopening and thus results in a particularly solid anchoring.

Hence the implant according to the invention makes it possible to exertpressure upon the lateral surfaces of the tissue opening. This enablesan anchoring of the implant even in situations where no or very littlepressure can be applied to the bottom of the tissue opening—e.g. becausethe bone is very brittle and/or very thin—or where the opening has nobottom because it is through-going. In such a case additional means forabsorbing the compressing force must be provided. Such means arediscussed in detail below.

The implant may be designed in various ways, wherein the compression ofthe implant is effected in corresponding various ways:

The implant consists of at least two separate components, wherein, dueto their geometry, the components are shifted relative to each otherunder the effect of the compressing force. Shifting occurs alongsurfaces that are neither parallel with nor perpendicular to thecompression axis but extend obliquely relative to the latter. Theimplant may be designed e.g. as a system of cones and/or wedges or as asystem with a spreader element, which does not necessarily need tocomprise thermoplastic material and e.g. is brought into the openingprior to the implant component(s) comprising thermoplastic material. Theenlargement of the cross sectional area is effected either by theshifting of the implant components relative to each other (e.g. wedgesystem) or by shifting the implant components relative to each other andsimultaneously spreading them (e.g. cone system).

The implant consists of at least two components linked via predeterminedbreaking points or predetermined liquefaction points, where thecomponents are separated from each other when the compression force, andpossibly also the mechanical vibrations, are applied. The requiredenlargement of the cross sectional area is effected by shifting of theimplant components relative to each other as described for the previousexample.

A separate element is provided in the opening for exerting a forcecounteracting the compressing force, wherein this element comprises asurface section which is oblique to the compression axis. The requiredlocal enlargement of the distance between the compression axis and theperipheral surface of the implant is effected by shifting the implant ora component thereof along the named surface, wherein the shiftedcomponent may or may not be spread.

The implant consists of one piece and comprises a section which isexpandable by the compressing force. The implant is e.g. shaped like ahollow truncated cone, a hollow wedge, a hat or a tube andadvantageously comprises slots to facilitate the expansion. Thecounterforce to the compressing force can be exerted on a surfaceperpendicular to the compression axis, or on a surface oblique to thecompression axis. The latter case constitutes a combination with one ofthe three aforementioned embodiments.

The implant comprises at least one buckling location designed as amechanically weak point (e.g. hole, slot, area of reduced wallthickness) or as a hinge. The local weak areas are softened during theimplantation procedure, causing implant portions between the weak areasto tilt towards each other under the influence of the compressing force.

In other words: the compressing force causes either just shifting of theimplant or of implant components (e.g. wedge systems), or shifting incombination with deformation (e.g. multi-part implants with spreadablecomponents) or just deformation (e.g. one-piece implant able to buckleor to be expanded). Therein the shifting and/or the deformation can besupported by an appropriately shaped tool and/or by a separate auxiliaryelement. In the case of multi-part implants it is advantageous to designcomponent surfaces, along which the components are shifted relative toeach other, thus, that they are welded together during implantation. Inthe case of implants or implant components to be deformed, it isadvantageous if the tensions caused by the deformation are resolvedunder the implantation conditions.

The implant or at least one of the implant components may comprise anelastically pliant, e.g. metallic (e.g. titanium) core; such a core maybe formed of sheet material and comprise an edge which, duringcompression, is moved radially outwards and thereby cuts into the bonetissue, providing an additional anchoring.

“Oblique to the compression axis” means at an angle less than 90° andmore than 0° relative to the compression axis. Advantageously, theoblique surfaces form an angle between 20° and 70° with the implant axisbefore implantation.

For physical reasons there is a counterforce to any acting force. If theopening in the bone tissue is a blind hole, the counterforce can beexerted by the bone tissue at the bottom of the opening. The inventionaccording to its first aspect (as well as according to the second andaccording to the third aspect described below) however, is alsoespecially suited to situations, where it is not possible or notdesirable that the bone tissue absorbs the acting force (or,synonymously, exerts the counterforce). In many relevant advantageous,embodiments the force is imposed between a tool and a counter-element(retaining element). The counter-element may be placed and held in sucha position that it does not transmit force to the bone tissue but thatthe force is exerted e.g. by the surgeon, by an assistant or by asuitable holder or device etc., whereas the implant is in contact withthe hard tissue/hard tissue replacement material, and the liquefactionof the liquefiable material occurs in contact with the hard tissue/hardtissue replacement material.

A preferred embodiment of the implant consists entirely of thethermoplastic material. It may however also comprise a non-liquefiablecore and still be compressible, e.g. if the core comprises severaltelescopic sheaths.

A second aspect of the invention provides a surgical device comprisingan implant suitable for being anchored in bone tissue with the aid ofmechanical vibrations as well as a tool (e.g. a sonotrode). The implantcomprises a coupling-in face through which the mechanical vibrations arecoupled into the implant and a material liquefiable by mechanicalenergy, which forms at least a part of the implant surface. The toolcomprises a proximal side and a distal side, wherein the distal toolside comprises a coupling-out face suitable for coupling the vibrationsout of the tool and adapted to the coupling-in face of the implant. Acoupling between the tool and the implant is designed to withstandtensile force (force in a direction from the distal tool side towardsthe proximal tool side). The implant is anchored in the opening with theaid of mechanical vibration and a pulling force (causing a tensile loadin the tool), whereby the thermoplastic material is at least partlyliquefied, where in contact with the bone tissue, and pressed into thebone tissue in order to form a form-fit connection with the bone tissuewhen re-solidified. Alternatively, the device further comprises acounter-element (retaining element) suitable for exerting a counterforce(direction opposite to the force exerted by the tool) by whichcounterforce the counter-element is put under tensile force.

A corresponding method of anchoring an implant in bone tissue comprisesthe following steps:

providing an opening in the bone tissue;

positioning the implant on the bone tissue thus that thermoplastic areasof the implant are in contact with the bone tissue;

coupling a force and mechanical vibrations via the coupling-in face intothe positioned implant, thereby liquefying at least part of theliquefiable material where it is in contact with walls of the openingand pressing it into the bone tissue in order to form a form-fitconnection with the walls after re-solidification,

wherein the force and the mechanical vibrations are coupled into theimplant with the aid of a tool, wherein a proximal tool side is designedfor mechanical vibrations to be coupled into the tool and the distaltool side comprises a coupling-out face through which the mechanicalvibrations are coupled into the implant, and wherein the force coupledinto the tool is a tensile force.

Whereas according to the state-of-the-art technology, a compressionforce is exerted on the tool for coupling a force into the implant.According to the second aspect of the invention, a tensile force isexerted on the tool for coupling a force into the implant. This verysimple measure opens up a lot of new possibilities, some of which areoutlined below:

Implantation in places difficult to access: the second aspect of theinvention allows under certain circumstances implantations to be carriedout from a non-accessible side.

Favoring a procedure which does not stress the bone tissue: by applyinga pulling force to the implant and counteracting it with a simplecounter-element—e.g. a simple perforated plate—practically all forcesacting on the bone tissue can be eliminated (except the force necessaryto ensure that the liquefaction of the liquefiable material can occurdue to the contact between hard tissue/hard tissue replacement materialand the implant surface).

Possibility of using newly developed implants and tools (sonotrodes).

For example, the coupling-out face of the tool faces “backwards”, i.e.towards the proximal tool side. This is the case e.g. when the normal ofthe coupling-out face extends approximately parallel to the direction ofthe tensile force.

Alternatively, the implant is drawn through the opening in the bonetissue, i.e. a tensile force or pulling force is applied to the implantand moves the implant to a certain extent inside the opening.

Particularly advantageous is a combination of the first and the secondaspect of the invention, i.e. the use of a compressible implantaccording to the first aspect in a device according to the secondaspect, which device is designed such that in action a tensile forceacts on the tool.

According to a third aspect of the invention, the implant is expanded bythe tool, i.e. by causing the tool to move, in an axial direction,within the implant and thereby locally expands it in a lateral directionthereby causing the lateral walls of the implant to be pressed againstwalls of an opening in the bone tissue or other hard tissue or hardtissue replacement material.

A method according to the third aspect, the method for anchoring animplant in bone tissue, where the implant comprises an axis as well as amaterial liquefiable by mechanical vibrations, which forms at least apart of the surface of the implant, accordingly, features the steps of

providing an opening in the bone tissue;

positioning the implant in the opening;

providing a tool having a proximal portion and a distal end portion;

positioning the tool in contact with the implant;

coupling the mechanical vibrations into the tool and simultaneouslymoving the implant relative to the implant in an axial direction, aportion of the tool moving in an interior of the implant, and therebyexpanding the implant and pressing the implant at least locally againstlateral walls of the opening and, due to the expansion and the effect ofmechanical vibrations coupled into the implant from the tool, liquefyingthe thermoplastic material at least partly where in contact with thewall of the opening to yield liquefied thermoplastic material, andpressing the liquefied material into the bone tissue in order to form apositive-fit connection with the wall after re-solidification.

The implant may comprise an axial implant opening, through which thetool (or a distal end thereof) is preferably moved.

A surgical device according to the third aspect of the inventioncomprises an implant suitable for being anchored in bone tissue with theaid of mechanical vibrations and a tool, which implant comprises an axisand an axially extending implant opening as well as a materialliquefiable by mechanical vibrations, which forms at least a part of thesurface of the implant, and which tool has a proximal portion and adistal end portion, wherein the distal end portion has at least onecross-section which is larger than at least one cross-section of saidrecess in the implant and which distal end portion is able to be movedwithin the implant opening relative to the implant under the influenceof a force and of the mechanical vibrations, whereby the implant islocally expanded under at least partial plastification of the implant,wherein the mechanical vibrations are able to be transmitted to aperipheral surface of the implant in the area of the expansion.

This means that embodiments of the third aspect of the invention arebased on the fact that, with the aid of the tool, the thermoplasticmaterial is liquefied or plastified in a peripheral implant region andadvantageously also in the area of the axially extending recess and ispressed radially outward. As with the procedure according to the firstaspect, with this procedure too an anchoring is achieved by means ofinterpenetration of bone tissue structures in a lateral wall of theopening in the bone tissue. Many relevant advantages and freedom ofdesign of the first aspect of the invention also apply to the thirdaspect of the invention.

According to a preferred embodiment of the third aspect of theinvention, the implant consists entirely of the thermoplastic materialor of a plurality of thermoplastic materials.

Particularly advantageous is a combination of the second aspect of theinvention and the third aspect, i.e. a procedure according to theteaching of the third aspect, wherein the force is coupled into the toolas a tensile force.

According to a further embodiment of the third aspect of the invention,the implant is expanded by the tool and therefore pressed against thelateral walls of the opening, is not anchored in these lateral walls bymeans of a liquefied material but by other means, e.g. by surfacestructures acting like barbs.

Objects of the invention are also sets of items for carrying out themethod according to one of the three aspects of the invention. Such aset comprises at least one tool (e.g. sonotrode) as well as one oradvantageously a plurality of implants. In addition, the set maycomprise a device for the generating the mechanical vibrations,instructions for the implantation, a counter-element (retainingelement), a separate element with an oblique surface area as discussedabove and/or further items.

In embodiments of any one of the three aspects of the invention, thetool may, after implantation, be removed, or it may remain in place and,for example, affixed to the implant by re-solidified material that wasat least partly liquefied during implantation. In the latter cases, thetool may, after implantation, serve as a functional part of the implant.It may for example be used in a load bearing manner, e.g. being a pin ora the load bearing part of a joint prosthesis, (stem), and may comprisemeans for affixing a further element to it such as a structure forforming a positive fit connection (such as a threading, a bayonetfixing, an eyelet for a thread or suture etc., or a structure which another element may be glued etc.

In embodiments that feature automatically applying the acting force, aswell as in other embodiments where the force is applied manually, theremay optionally be a stop defining the travel of the tool duringimplantation.

The methods and implants described herein may be used for connecting twoparts of the human or animal skeleton, or for connecting one part of theskeleton and a soft tissue part, or for connecting at least one part ofthe skeleton and another object. The implants described herein may alsobe endoprostheses such as e.g. joint prostheses, bone prostheses,intervertebral disc prostheses, artificial ligaments or tendons,artificial teeth, etc. According uses of implants as such are known inthe art, and the methods and implants according to the invention maydiffer from known methods and implants primarily in their structure andin the here-described way the connection to the hard tissue is achieved.Alternatively, the methods and implants may also be used for newapplications in surgery, some of them being only made possible by theinvention according to any one of the above-described aspects.

Some of the new applications of implants are described in this text.These applications described herein are mere examples of new uses theapproach according to the invention makes possible, the new applicationsbeing by no means restricted to the described examples.

A category of applications concerns the re-surfacing of joint parts.Examples of re-surfacing techniques have for example been described inU.S. provisional patent application No. 60/913,012, that is incorporatedherein by reference. According to re-surfacing applications, an elementis fixed to remaining bone material by an implant according to anyaspect or combination of aspects of the invention. The element maycomprise a coating replacing the cartilage of the joint part, or such acoating may be applied to the element after its fixation.

Another category of applications is the fastening of support elements(such as screws or plates) fixing the relative position of bonefragments after a fracture or after insertion of bone replacementfragments or bone replacement material. Such a support element may,according to the present invention, be fixed, in one or more locations,by an implant according to any aspect or combination of aspects of theinvention.

An even further category of applications is the replacement ofconventional surgical screws by implants according to any one of theaspects of the invention or according to any combination of aspects.

Yet another category of applications concerns the anchoring of a sutureby means of an implant according to any aspect or combination of aspectsof the invention. The suture may be fixed to the implant (or an elementfixed by the implant) prior to implantation, by implantation, or it maybe fixable to such element after implantation.

In the following, embodiments of the invention are described inconnection with the following Figures, wherein the same referencenumerals are used for same or equivalent elements. Therein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1a and 1b illustrate a first embodiment of the invention accordingto its first aspect;

FIGS. 2a and 2b show a sectional view of the embodiment according toFIGS. 1a and 1b in an opening in the bone tissue to illustrate itsfunction;

FIGS. 3a to 3c are sectional views (not showing the contact with thebone tissue) of further embodiments of the invention according to itsfirst aspect;

FIG. 4 is a sectional view of the embodiment according to FIG. 3a in aconfiguration which also corresponds with the second aspect of theinvention;

FIG. 5 is a sectional view of a further embodiment of an implant in anopening in the bone tissue;

FIG. 5a is a sectional view of an even further embodiment of an implantin an opening in the bone tissue;

FIG. 6 is a sectional view of a further embodiment of an embodiment ofthe invention according to its first aspect;

FIG. 7 illustrates the functional characteristics of a further group ofembodiments;

FIGS. 8a and 8b show a further embodiment of the invention according toits first aspect;

FIG. 9 shows a further embodiment of the invention according to itsfirst aspect;

FIG. 10 shows an embodiment of the invention according to its firstaspect, wherein the implant comprises a non-liquefiable core;

FIG. 11 shows a further embodiment of the invention according to itsfirst and second aspect;

FIGS. 12a to 12d illustrate the principle of a device and a methodaccording to the second aspect of the invention;

FIGS. 13, 14 a, 14 b show further embodiments according to the secondaspect of the invention;

FIGS. 15 and 16 show embodiments of a combination of the second aspectand the third aspect of the invention;

FIG. 17 illustrates a further embodiment according to the third aspectof the invention;

FIG. 17a shows the embodiment of FIG. 17 after implantation;

FIG. 18 illustrates the principle of a distal counter-element;

FIG. 19 shows a coupling suitable for transmission of a pulling force;

FIG. 20 illustrates yet a further variant of an implant and methodaccording to the first aspect of the invention;

FIGS. 21a and 21b show yet another embodiment of the invention;

FIGS. 22a and 22b show a further embodiment of the third aspect of theinvention;

FIGS. 23a and 23b show yet another embodiment of the third aspect of theinvention;

FIG. 24 shows a variant of the embodiment of FIGS. 23a and 23 b;

FIGS. 25a and 25b illustrate the principle of the fixation of a screwreplacement implant; and

FIG. 26 illustrates a possibility of resurfacing a joint using animplant according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

The implant 1 according to FIG. 1a is a first example of an implantaccording to the first aspect of the invention. The implant isessentially tubular, consists of a thermoplastic material, and comprisesa proximal end face 1.1 and a distal end face 1.2. The implant furthercomprises at least one slot 12 extending approximately parallel to theaxis 11 of the implant; advantageously there are two, three or more thanthree slots arranged approximately equidistantly. Due to the slot orslots 12 the implant is compressible by a compressing force 4 actingparallel to its axis (according to FIG. 1a , the axis 11 of the tubularimplant is also its compression axis). The implant is depicted in acompressed state in FIG. 1 b.

It is obvious that for achieving the desired compression, a force mustact upon the implant from two opposite sides (“force and counterforce”),wherein the counterforce is often exerted by a stop face. In theembodiment according to FIGS. 1a and 1b compressing forces are exertedupon the proximal end face 1.1 and the distal end face 1.2. In thefollowing description however, a force is illustrated only where a toolis in action. To the expert it is obvious that a counterforce must existin order to achieve the desired effect.

According to the invention the implant is designed thus its compressionresults in a local enlargement of the distance between the peripheralimplant surface and the compression axis 11, here, a local enlargementof the exterior cross-section perpendicular to the compression axis 11.The enlargement can occur anywhere between the proximal end face 1.1 andthe distal end face 1.2. In the example according to FIGS. 1a and 1b theenlargement is, due to the symmetry of the implant, greatest in themiddle between the end faces. In FIGS. 1a and 1b , the diameter of theouter cross section—this also incorporates the cavity within theimplant—is indicated at the point of the largest cross section by c inthe non-compressed condition, by c′ in the compressed condition. Throughthe compression, the slots 12 become wider.

For implantation, the implant 1 is placed in an opening 21.1 in bonetissue 21. As illustrated in FIG. 2a this opening can be a blind bore.Alternatively the opening is tunnel-shaped, i.e. reaches through thebone (for more detail see further below). In particular, the opening canbe of a cylindrical shape, which is easy to be made. The diameter of thebore is at least equal to the diameter c of the outer cross section ofthe original outer cross section and may be slightly larger, as shown inFIG. 2 a.

When the implant is positioned in the opening 21.1, a force 4 is exertedalong its compression axis 11 and mechanical vibrations 5 are coupledinto the implant while the force 4 is active. This is achieved with theaid of a tool 3 comprising a coupling-out face 3.1, which collaborateswith a coupling-in face of the implant. In the illustrated example thecoupling-in face corresponds with and is identical with the proximal endface 1.1. The coupling-out face 3.1 can completely cover the proximalend face 1.1 and the interior cavity of the implant 1, as shown, but itcan also be ring-shaped and exactly adapted to the proximal end face1.1. The tool 3 is effectively connected on its proximal side 3.2 with avibratory device (not shown). Such devices are generally known and havebeen referred to e.g. in WO02/069817.

FIG. 2b shows the implant 1 after application of the compressing forceand the vibrations. Due to the compressing force 4 the cross-section ofthe implant is enlarged, as illustrated in FIG. 1b . As soon as theimplant engages in areas of the cross-section enlargement with thelateral wall of the opening, the compressing force 4 produces a pressureupon the lateral walls. There the vibrations cause friction and thethermoplastic material is locally liquefied and pressed into pores orother cavities in the bone. This effect is indicated by horizontalarrows in FIG. 2b . Of course the same also occurs in the area of thedistal end face of the implant.

Once a predetermined compression is achieved, the vibrations areswitched off and/or the tool 3 is removed. The liquefied thermoplasticmaterial re-solidifies and creates an anchoring of the implant 1 througha form-fit connection with the structures of the lateral wall.

The method of anchoring the implant with the aid of thermoplasticmaterial which is liquefied and in the liquefied state penetrates intocavities (pores, other cavities of small dimensions when compared withthe opening provided in the bone tissue for the implant), which methodis illustrated in FIG. 2b , is shared by all the embodiments of theinvention. In each following Fig. this effect is illustrated by arrowsindicating the direction in which the thermoplastic material penetratesinto the cavities.

Preferably but not necessarily, as in all embodiments according to thefirst aspect of the invention, the thermoplastic material of the implantis heated during the implantation procedure to such an extent that it isfree of tension after the implantation procedure, i.e. no forcecounteracting the implant deformation remains. In this case thecompressing force and the mechanical vibrations can be stoppedsimultaneously as the implant does not relax, neither before nor afterre-solidification.

The implant 1 according to FIG. 3a comprises a plurality of components.The illustrated example consists of three components 1.11, 1.12, 1.13,which are approximately rotationally symmetrical with regard to anyrotation angle around its axis, which also corresponds with thecompression axis 11. The first component 1.11 (seen from the distalside) has essentially the shape of a truncated cone and comprises anaxial bore through it. The second component 1.12 has essentially theshape of a hat, here with a central axial bore. The hat-like designdefines an interior surface 1.12 a and an exterior surface 1.12 b. Thethird component 1.13 has the shape of a cylinder and comprises a coaxialconical cavity and an axial bore. The central bores of the first, secondand third component are coaxial to each other and of approximately thesame diameter.

If applicable and deviating from the rotational symmetry, at least thecentral component 1.12, but possibly also the third component 1.13 andthe first component 1.11, are advantageously slotted, which is not shownin FIG. 3a . Because of the slot(s) the relevant components are easilyspreadable and the implant as a whole can be compressed along thecompression axis by a relatively moderate compressing force. As thecompressing force 4 is applied the components 1.11, 1.12, 1.13 areshifted relative to each other along surfaces extending obliquely (i.e.at an angle or neither parallel nor perpendicular) to the compressingforce. In the illustrated embodiment, the named surfaces have the formof truncated cone shells, i.e. they are conical. There are othersurfaces also which have a spreading effect.

In the illustrated embodiment, the opening angle of the exterior surface1.11 a of the first component 1.11 is larger than the opening angle ofthe interior surface 1.12 a of the second component 1.12 and the openingangle of the exterior surface 1.12 b of the second component 1.12 islarger than the opening angle of the interior surface 1.13 a of thethird component. Advantageous for the spreading effect in the presentconfiguration is that at least one opening angle of an exterior surfaceis greater than the opening angle of an interior surface, into which theexterior surface reaches.

When the implant is positioned in the opening in the osseoustissue—diameter of opening approximately corresponding with the outerdiameter of the implant components 1.11, 1.12, 1.13 beforecompression—and when compressing force and mechanical vibrations areapplied, the following takes place:

Due to the compressing force, the second and the third component 1.12,1.13 are spread, resulting in an enlargement of the outer crosssectional area of the second and third component and thus of the wholeimplant.

Due to the spreading outer surfaces, the second and third component1.12, 1.13 are pressed against the lateral wall of the opening. Due tothe mechanical vibrations the thermoplastic material liquefies in thesesurface areas and interpenetrates the pores (or other cavities) in theosseous material 21.

The vibrations also result in frictional forces between the surfaces1.11 a, 1.12 a, 1.12 b, 1.13 a which cause the thermoplastic material toliquefy, which in turn results in the first, second and third componentsbeing welded together.

The proximal end face 1.1 or alternatively, the distal end face 1.2 ofthe implant according to FIG. 3a can serve as a coupling-in face. Theproximal and the distal side of the implant can be exchanged (i.e. theimplant can be used “back to front”).

FIG. 3b shows a further embodiment of the implant according to theinvention, which implant is, regarding compression and implantation,very similar to the embodiment according to FIG. 3a . Same elements aredesignated with same reference numerals. The implant is a multi-partimplant and consists of any chosen number (e.g. three as shown) ofidentical components, all designed for being spread (e.g. hollow conesor hollow wedges) and loosely positioned inside one another. Thecompressing force 4 pushes the spreadable components together andspreads them. If need be, the distal end portion of a tool to be used isdesigned as a spreading element, as illustrated in FIG. 11. In theembodiment according to FIG. 3b all surfaces oblique to the compressionaxis, along which the implant components are shifted in relation to eachother, may be parallel (identical opening angles), as illustrated inFIG. 11. This has the advantage that a user—e.g. a surgeon—can determinethe size of the implant by choosing the number of identical components.

The embodiment according to FIG. 3c is based on the embodiment accordingto FIG. 3a . Unlike that embodiment however, the implant consists of aplurality of modules (illustrated: two modules) each of which comprisesat least one component 1.11, 1.12, 1.13, 1.14 (illustrated: twocomponents per module). There is a spacer element 61 between themodules, e.g. illustrated as a metallic ring, which does not need to beof thermoplastic material. This embodiment is suitable for beinganchored at two or more locations in a lateral wall of the opening inthe bone tissue. The distance between these locations is determined bythe spacer element. Such implant embodiments comprising two modules areadvantageously used in combination with a tool 3 or counter-element 31,whose function is discussed in more detail below. As shown in FIG. 3c ,the tool or counter-element 3,31 comprises a shaft penetrating a centralrecess of the implant. Other guiding means for guiding the spacerelement are conceivable.

In addition to the embodiments illustrated in FIGS. 3a, 3b and 3c , thefollowing embodiments (besides many others) are conceivable:

Each component may comprise a non-liquefiable core, the core of thesecond and third component being elastically or plastically deformable.The core, which e.g. consists of titanium, may constitute a substantialpart of the cross-section and form the load-bearing part of the implant.

The first component 1.11 does not necessarily need to comprisethermoplastic material.

The first component may be removable after implantation (in which caseit is not part of the implant but e.g. part of the tool or a separateelement).

An equivalent embodiment comprises instead of three components only twocomponents (e.g. no central component 1.12) or four or more than fourcomponents (e.g. further hat-shaped components similar to the centralcomponent 1.12).

The shapes of the components may be varied, wherein it is necessary toprovide some surfaces oblique to the compression axis, along whichsurfaces the components are able to be shifted relative to each other.

The components do not need to be approximately rotationally symmetrical.The central bore may be omitted.

The components may be linked prior to the implantation via predeterminedbreaking points, which will be discussed in more detail below.

The components do not need to be hat-shaped and able to be spread butmay be laterally displaceable relative to each other, which is alsodescribed in more detail below.

For a selective liquefaction of thermoplastic material in a desiredlocation, at least one energy director may be provided along theperiphery of at least one component.

The embodiments according to FIGS. 3a to 3c , the same as theembodiments according to the first aspect of the invention as describedbelow, may comprise an elastically ductile core of a material, which,under implantation conditions, is non-liquefiable. At least the implantswith components which have the shape of hats or hollow wedges can e.g.be made of sheet metal which is slotted and coated with thermoplasticmaterial, wherein the metal sheet may protrude radially from the implantcomponent. During compression, the metal sheet is spread and cuts e.g.into the bone tissue of the lateral wall of the opening. The implant maybe additionally furnished with elements acting like barbs. The cuttingeffect of the metal sheet provides an additional anchoring.

Any chosen combinations of the named embodiments are possible.

In FIG. 4 the implant 1 according to FIG. 3 is shown in a configurationcorresponding with the second aspect of the invention. In thisconfiguration, no force is exerted on the bone tissue on the bottom ofthe opening. The vibrations and the compressing force acting upon theimplant are coupled into the implant from a tool 3 which is undertensile force. The configuration according to FIG. 4 is therefore alsosuitable for applications in tissue openings leading tunnel-like throughthe bone tissue.

The tool 3—as it serves among other things to couple vibrations from avibratory device (not illustrated) into the implant, it can also becalled a ‘sonotrode’—comprises a shaft 3.4 and a base plate 3.5. Theshaft and/or the base plate can make up a substantial part of thecross-section of the device consisting of tool and implant and can beleft in the implant to form the load-bearing implant part. For suchpurposes, the shaft and/or base plate are made, e.g. of titanium. Thecoupling-out face 3.1 of the tool is the surface of the base plate 3.5facing towards the proximal tool side. The shaft 3.4 extends through thecentral bore of the implant-components 1.11, 1.12, 1.13 and protrudesfrom the proximal end of the implant and from the opening in the bonetissue. The proximal tool end is designed for being coupled to avibratory device, which coupling is to be suitable for transmitting atensile force.

During the implantation procedure, a tensile force is applied to thetool 3 (force 4) and mechanical vibrations 5 are coupled into it. Fromthe tool, force 4—as compressing force—and the mechanical vibrations arecoupled into the implant. A counter-element 31 prevents the implant fromsimply moving out of the opening in the bone tissue. In the illustratedexample the counter-element 31 is designed as a plate.

Following the implantation procedure, the tool 3 can be dealt with invarious ways:

The tool can remain in the place of the implantation. This embodiment isparticularly advantageous when the tool is designed for a furtherfunction. Thus the tool can serve e.g. for attaching a further elementon the implant, e.g. a suture, a ligament, a tendon, another bone, anendoprosthesis or any other element. The tool can be designed forpractically any function known to be functions of implanted objects.

If the opening in the bone tissue is a through-going opening, the toolcan be separated from the vibratory device and be removed from thedistal side of the implant.

The tool can be removed from the proximal side. In this case the tooland the through-going recess in the implant, through which the shaft 3.4extends during the implantation procedure, must not be of a round crosssection (no rotational symmetrical with regard to random rotationangles). Corresponding implant openings will be discussed in more detailbelow.

Like the implants according to FIGS. 1 and 3, the implants according tothe FIGS. 5 to 10 are designed according to the first aspect of theinvention and can be used together with a suitable tool in aconfiguration according to the second aspect of the invention.

The implant 1 according to FIG. 5 comprises, like the one according toFIG. 3, a plurality of components 1.11, 1.12, 1.13, which are designedfor being shifted relative to each other along surfaces that extendobliquely (i.e. at an angle or neither parallel nor perpendicular) tothe compressing force. The components can be designed just like theimplant components—in particular the second and/or third component—ofthe embodiment according to FIG. 3 and its variants and are thereforenot described in detail again. In contrast to the embodiment accordingto FIG. 3, a separate spreading element 32 is used, wherein thespreading element does not need to comprise thermoplastic material. Asillustrated, the spreading element is placed on the bottom of theopening in the bone tissue 21 before the implant is introduced. Thespreading element comprises at least one shifting surface 32.1, which isoblique relative to the compression axis and forms an angle with thelatter which is greater than the opening angle of the correspondinginterior surface 1.13 a of the implant. The components 1.11, 1.12, 1.13are spread by the compressing force 4 due to the effect of the spreadingelement and in the area of their circumference are pressed against thelateral wall of the opening in the bone tissue. During the implantationprocedure, the spreading element can be welded to the components 1.11,1.12, 1.13 comprising thermoplastic material such becoming part of theimplant. Depending on the surface properties, the spreading element mayalso remain separate. In the illustrated configuration the spreadingelement remains in the opening in the bone tissue where it may or maynot have a medical function. In other configurations it may be removablefrom the opening.

The spreading element—whether or not it comprises material liquefiableduring implantation—may optionally be configured to be connected to theimplant 1—and to become part of it—during implantation, for example bywelding and/or by other means of forming a connection.

The following embodiments are conceivable in addition to the previouslydescribed embodiments:

Instead of three components there may be a single component, twocomponents or four or more components, comprising thermoplastic materialat least in a peripheral region.

The implant may also be placed the other way round, provided that theexpansion element is correspondingly adapted.

Combinations with the variants as described in connection with theembodiment of FIG. 3 are possible.

The spreading element may be omitted, in which case the implantcomponents are placed upon a surface approximately perpendicular to thecompression axis—e.g. the bottom of the opening—which surface exerts thecounterforce. This embodiment is equivalent to the one shown in FIG. 3b.

FIG. 5a shows a variant of the embodiment of FIG. 5. It differs in thatthe spreading element 1.12—being a second part of the implant—is made ofthermoplastics and is welded together with the first implant part 1.11during the implantation process. The first implant part 1.11 comprisestwo legs 1.21, 1.22 that are spread apart by the spreading element 1.12.

The depicted first implant part 1.11 further comprises, at its proximalend, a thermoplastic implant head with a larger cross section than amain portion of the implant.

Of course, also combinations of the approaches of FIGS. 5 and 5 a arepossible, for example a first implant part with two legs 1.21, 1.22 tobe spread apart may be combined with a spreading element of notthermoplastic material, or a spreading element 1.12 of thermoplasticmaterial may be combined with a first implant part with a slittedhat-like distal end portion etc.

FIG. 6 shows yet another variant of the embodiment according to FIG. 5.This differs from the latter by not comprising a separate (spreading)element with a surface section oblique to the compression axis. Instead,spreading is achieved by the shape of the implant 1 and by the implantbeing pushed against an e.g. level surface perpendicular to thecompression axis, which may be the bottom of the opening in the bonetissue as illustrated, or the surface of a separate element. In theillustrated example, the implant is hat-shaped and the compressing force4 squeezes the edges outwards, thus, pressing them against the lateralwalls of the opening. Advantageously the hat-shaped implant comprises aslot or a plurality of slots as described further above. Variants withother spreadable shapes (e.g. hollow wedge) are also conceivable.

FIG. 6 moreover illustrates, that the tool 3 can be of a specific shapeadapted to the coupling-in face 1.1—here at least on the distal sidetubular. Such a specific shape enables an energy-efficient coupling ofmechanical vibrations into the implant.

The embodiment of the implant 1 according to FIG. 7 comprises twocomponents. A first proximal component 1.11 is connected to the seconddistal component 1.12 by connecting fins 1.21, which are thin comparedto the dimensions of the implant. During compression of the implant thefins 1.21 break or melt, i.e. they represent predetermined breaking ormelting points. The first component 1.11 and the second component 1.12are wedge-shaped, each comprising a ramp 1.11 a and 1.12 a which slidesideways along each other when the components are pressed against eachother by a compressing force acting along the compression axis 11.

After disintegration of the connecting fins 1.21, the implant components1.11, 1.12 are shifted relative to each other under the influence of thecompressing force. The embodiment according to FIG. 7 is therefore afurther example of an implant comprising a plurality of components 1.11,1.12, movable relative to each other along surfaces (i.e. ramps)extending obliquely to the compression force. In this embodiment too, anouter diameter of the implant is enlarged by the lateral shift caused bythe compressing force.

Connections like the connecting fins 1.21 serving as predeterminedbreaking or melting points can, as already mentioned, also be applied inthe multi-part embodiments discussed further above.

The design of the shifting surfaces oblique to the compression axis 11as ramps—with or without connections between the components—may also becombined with the characteristics of the embodiments of FIGS. 3 and 5.

In particular one of the implant components may be replaced by aseparate element which does not need to comprise thermoplastic materialand functions in an analogous manner as the spreading element accordingto FIG. 5.

Alternatively to the illustrated embodiment, an implant according toFIG. 7 can also be designed to be thermoplastic and essentiallycylindrical (e.g. circular cylinder) with horizontal (i.e. perpendicularto the cylinder axis) or oblique incisions, which do not reach rightthrough the implant but leave areas of a reduced cross section. Theseserve as predetermined breaking or melting points. Such an embodimentmay be advantageous with regard to production.

FIG. 8a shows a further embodiment of an implant 1 according to theinvention. In this embodiment, as opposed to the previously describedembodiments, the local enlargement of the distance between a peripheralsurface and the compression axis is not necessarily due to anenlargement of the exterior cross sectional area. In this and othersimilar examples however, at least the projection of the exteriorsurface along the compression axis is enlarged.

The implant is essentially pin-shaped, but comprises lateral incisions14, 15 and corresponding contractions 1.4, 1.5. During implantationthese contractions function as predetermined melting points. As theymelt, or at least soften, due to the effect of the mechanicalvibrations, the compressing force tilts the implant sections between thecontractions towards each other such effecting the local enlargement ofthe distance between the peripheral implant surface and the compressionaxis, as shown in FIG. 8b , which illustrates schematically the shape ofthe implant after implantation. The regions being pressed against thelateral walls of the opening in the bone tissue are indicated byhorizontal arrows. The effect of liquefaction (the liquefied materialbeing pressed into structures of the bone material) then takes placewhere the implant is pressed against the lateral wall.

Alternatively, the implant may comprise just one contraction 14, or twocontractions (or possibly more than two contractions) with differingcross-sections. In particular the implant may comprise a widercontraction closer to the coupling-in face. This can result in thecontraction further removed from the coupling-in face liquefying beforethe contraction closer to the coupling-in face and may prevent thecontraction closer to the coupling-in face from melting before the othercontraction, which would inhibit further transmission of mechanicalvibrations to this other contraction.

FIG. 9 shows an embodiment of an implant 1 according to the inventiondesigned in the manner of an accordion, wherein portions 1.31 linked byhinges 1.32 are moved into a steeper position in relation to thecompression axis 11 under the influence of the compressing force 4.Thereby the outer cross-section of the implant is enlarged locally. Inthe illustrated embodiment the whole implant 1 is a single unit, so thatthe hinges 1.32 are created simply by the shape of the implant body; theuse of other hinging means is possible. In certain circumstances,measures can be taken to enable mechanical vibrations to be transmittedto the areas further removed from the coupling-in face. Such measuresare e.g. the provision of a non-liquefiable core of superior rigiditycompared to the thermoplastic material.

Such a core is shown in FIG. 10 in an embodiment similar to the one ofFIG. 3. Elements equivalent to the corresponding elements of theembodiment according to FIG. 3 are not again described in detail. Thecore comprises two core components 41, 42, which are moveable againsteach other. The first core component 42 comprises, in the illustratedembodiment, a base plate 42.2 and an adjoining sheath-like section 42.1.The exterior or interior surface of the base plate 42.2 can serve as acoupling-in face for the mechanical vibrations. The second corecomponent 41 is here designed as a sheath moveable inside thesheath-like section 42.1 of the first core component. While the implantis compressed one core component slides inside the other.

Alternatively to the two-part core, one-piece cores or multi-part coresare also possible. A one-piece core does not extend across the entirelength (relating to the compression axis 11) of the implant, becausethat would render a compression of the implant impossible.

FIG. 11 shows a configuration with a compressible implant 1 according tothe invention of the kind described in connection with FIG. 5. Incontrast to the latter, there is no separate spreading element but thetool 3 comprises a wedge- or ramp-like coupling-out face 3.1 that isformed by a distal end portion 3.7 being larger in diameter than a shaftportion 3.4. The wedge- or ramp-like coupling-out face 3.1 serves tocouple mechanical vibrations and the compressing force into the implantas well as to spread the implant.

In the configuration illustrated in FIG. 11, moreover, the principle ofthe tool 3 under tensile force is applied. The configuration accordingto FIG. 11 is therefore also suitable for use in tissue openings with abottom which is not suitable to be loaded or in a through-going opening(tunnel) as illustrated in FIG. 11.

The principle of coupling a force into the implant which puts the toolunder tensile loading corresponds with the second aspect of theinvention. This principle can also be applied in connection withimplants which are not compressed by the named force. Suchconfigurations are described in connection with the following FIGS. 12to 16.

FIGS. 12a and 12b show, in section and viewed from the top, a bonetissue 21 comprising a slot-shaped (not round) opening 21.1 reachingtunnel-like from one surface to the opposite one. FIG. 12a also shows atool 3 with a shaft 3.4 and a reach-out portion. In the illustratedembodiment the reach-out portion is a traverse 3.6 orientedperpendicular to the shaft. Two implants of thermoplasticmaterial—possibly with a solid non-thermoplastic core—are fixed to thetraverse 3.6 in a reversible manner.

As illustrated in FIG. 12a , the tool 3 with the implants attachedthereto is moved in a first step from a proximal side of the bonethrough the opening until the implants 1 are completely outside the bonetissue. Subsequently, as shown in FIG. 12c , the tool is rotated aroundan axis defined by its shaft 3.4, e.g. by 90°. Then, as in thepreviously described embodiments, a force is coupled into the implantspressing the thermoplastic material of the implants against the bonetissue. This is achieved by pulling the tool backwards, thereby pressingthe implants against the rear side of the bone tissue. While the forceis acting upon the implants, mechanical vibrations are coupled into theimplant via the coupling-out face 3.1 of the tool, which is here theproximal surfaces of the traverse upon which the implants are fixed.This causes the thermoplastic material of the implants to partly liquefyand to be pressed into the bone tissue. After stopping the mechanicalvibrations, the thermoplastic material re-solidifies and forms aform-fit connection with the bone tissue.

As shown in FIG. 12d the tool is subsequently removed by being detachedfrom the implants now anchored in the bone tissue by a gentle push. Thenit is turned back into the orientation in which the reach-out sectionfits through the opening 21.1 and is retracted. Alternatively to theillustrated embodiment, it is also possible that the tool is left in thebone tissue after implantation and there e.g. assumes another function.It is also possible to remove just a part of the tool, e.g. the shaft,while another part, e.g. the reach-out portion, remains and assumes afurther function. In such a case the tool is not a single unit but shaftand reach-out portion are attached to each other in a reversible manner,e.g. by being screwed together.

The embodiment of the invention shown in FIGS. 12a to 12d is alsosuitable for securing two pieces of bone, which, prior to theimplantation, are separated from each other or connected only by a weaklink, together from “behind”, i.e. from a side not easily accessible. Insuch a case the tool is not introduced through an opening as illustratedin FIG. 1b but through the gap between the two bone sections. Thereach-out portion of the tool remains in place after the implantationand serves as a bridge connecting the two bone sections in a rigidmanner.

In the illustrated embodiment, no openings are provided in the bonetissue for positioning the implants prior to the application of themechanical vibrations. The opening 21.1 in the bone tissue merely servesfor positioning the tool. The implants are driven into the bone tissueby a force exerted upon them, wherein an implant tip and/or axiallyextending cutting edges, advantageously not consisting of theliquefiable material, support penetration of the implant into the bonetissue.

The force for driving the implants into the bone tissue can e.g. beapplied before the mechanical vibrations. Alternatively to theillustrated configuration, it is also possible to provide openings inthe bone tissue, wherein the diameter of these openings may be smallerthan the diameter of the implants.

The following variants are possible:

Instead of with two implants as illustrated, the method can also beperformed with just a single implant or with more than two implants.

The reach-out portion of the tool can have any shape optimized for itsfunction as well as for the transmission of vibrations and force.

Depending on circumstances the tool with the implants can be introducedfrom behind (i.e. from the distal side) so that only the shaft has to bemoved through the opening in the bone.

FIG. 13 shows a further embodiment of the invention. A through-goingopening having a constant cross section (e.g. a through-bore with around cross section) is provided in the bone tissue 21. An implant 1tapering from the distal side to the proximal side is introduced frombehind, i.e. from the distal side into the opening. The implant is drawninto the opening with the aid of the tool 3, which engages the proximalside of the implant, wherein a tensile force acts on the tool (the toolis under tensile loading). While the tensile force is kept active themechanical vibrations are coupled into the implant. The vibrations andthe slightly tapering shape of the implant cause the thermoplasticmaterial in the area of the circumferential surface of the implant to beliquefied and to be pressed into pores or other cavities on the lateralwalls of the opening in the bone tissue.

In this embodiment, where tensile forces not only impinge on the toolbut also on the implant, it is necessary to connect the tool and theimplant rigidly, as described in more detail below.

As a—often less preferred—variant, the opening may taper toward theproximal side while the implant is cylindrical.

As a further variant, the opening in the bone tissue can be stepped,wherein it is wider on the distal side than on the proximal side. Thecorresponding implant may comprise a shoulder engaging the step of theopening during the implantation procedure. Further embodiments ofimplants, which can be implanted by means of pulling force, areconceivable.

FIG. 14a shows a configuration with a slightly conical implant 1 beingmoved, like the implant according to FIG. 13, with the aid of a tool 3along an axis of the opening in the bone tissue, wherein the force to becoupled into the implant puts the tool under tensile force, i.e. theforce acting on the implant is directed against the oscillationgenerator. However, in contrast to the configuration according to FIG.13 the force upon the implant 1 is a pushing force and pushes theimplant into the opening. To this end the implant comprises a centralbore (recess) 1.9, which in the illustrated configuration extendsparallel to the axis of the opening in the bone tissue during theimplantation procedure. A tool shaft 3.4 carrying a base plate 3.5extends through the bore 1.9. The force to be coupled into the implantas well as the mechanical vibrations are transmitted from the tool tothe implant via the base plate, the same as shown in FIG. 4. After theimplantation there are three ways of dealing with the tool.

Firstly, provided the opening in the bone tissue is a through-goingopening, the tool is separated from the oscillation generator andremoved towards the distal side. Secondly, the tool is also separatedfrom the oscillation generator and remains with the implant, where itfulfils a predetermined function, e.g. serves for attaching a furtheritem. Thirdly, the tool is dismantled after the implantation, e.g. theshaft 3.4 is separated from the base plate 3.5.

The following variants are conceivable:

The cross-sections of the opening in the bone tissue and of the implantare not circular.

The tool is removable as a whole toward the proximal side if thecross-sections of the recess 1.9 and of the base plate 3.5 are notcircular and the base plate 3.5 is able to be moved through the recess1.9 in one specific rotational position.

The implant is not necessarily conical. Thus e.g. the opening in thebone tissue can get narrower toward the proximal side. While providingsuch an opening is generally difficult, there may still be cases inwhich this is favored by natural circumstances.

It is also possible that the implant as well as the opening in the bonetissue are e.g. cylindrical, i.e. their cross-sections remain constantalong their axes. Then the cross-section of the implant would beslightly larger than that of the opening in the bone tissue, so that theimplant is held in the opening by a press-fit. The frictional force maybe strong enough to act as counter force to the force coupled into theimplant by the tool. Alternatively a counter-element can be used in thisembodiment.

A further embodiment is illustrated in FIG. 14b . The implant 1 has ashoulder 1.10 being pressed against an equivalent shoulder of the bonetissue during implantation. In the illustrated case, the mouth of theopening forms the shoulder of the bone tissue, however it could also bedesigned as stepped or otherwise designed widening of the opening. FIG.14b is a further example of an embodiment of the second aspect of theinvention, in which the anchoring does not necessarily occur in thelateral walls of the opening.

The following FIGS. 15 to 17 show embodiments according to the thirdaspect of the invention. The configurations in the examples according toFIGS. 15 and 16 correspond also with the second aspect of the invention.

In the configuration according to FIG. 15 a through-going or blindopening is provided in the bone tissue 21 in which the implant isintroduced prior to the implantation. The implant 1 comprises athrough-going or blind recess. The tool 3 comprises a shaft 3.4 (shaftportion) and a wedge 3.7 (distal end portion) tapering from the distalto the proximal side, where it is attached to the shaft. Duringimplantation a pulling force 4 causes the wedge to be drawn through therecess of the implant 1 thereby expanding the latter. Thus a peripheralarea of the implant is pressed against a lateral wall of the opening inthe bone tissue. The mechanical vibrations, being coupled simultaneouslyinto the implant, cause the thermoplastic material to liquefy where itis in contact with the bone tissue and to be pressed into cavities inthe bone tissue. Advantageously the mechanical vibrations also cause thethermoplastic material to at least soften between the recess and theperipheral area. This softening leaves the implant free of tension afterthe removal of the tool, such preventing forces directed radiallyinwards acting on peripheral areas anchored in the bone tissue.

While the pulling force is exerted upon the tool a counter-element 31prevents the implant from being drawn out of the opening. In theillustrated example, the implant 1 comprises peripheral, here pointedenergy directors 1.8, which assist liquefaction of the liquefiablematerial. Energy directors can also be provided on implants according toother embodiments of the invention described in this document.

FIG. 16 shows an embodiment similar to the one of FIG. 15, wherein thetool is of a different shape. Instead of a wedge, the distal end portionof the tool is e.g. fashioned like a spherical swelling 3.7. Duringimplantation this distal end portion is drawn through the implant whilethe thermoplastic material is liquefied and causes an advantageouslyplastic expansion of the implant as in the example according to FIG. 15.

Alternatively the tool may comprise instead of a shaft 3.4 a a non-rigidelement, e.g. a thread or a cable for pulling the distal end portionthrough the implant. The distal end portion may again be a sphericallike in FIG. 16.

Further alternatives are conceivable:

A thickened distal end portion 3.7 of the tool can have many differentshapes; the largest cross-section of the distal end portion must alwaysbe larger than the smallest cross-section of the recess in the implantand smaller than the cross-section of the opening in the bone tissue.

The recess of the implant 1 does not need to be through-going; moreoverthe tool can already be positioned in the recess designed as a blindhole prior to the implantation procedure and is then moved within orwithdrawn from this recess during the implantation procedure. Theadvantage of such a configuration is the fact that the appropriate toolcan be sold and stored together with the implant and the tool can alsoassist in positioning of the implant.

The opening in the bone tissue can either be through-going or blind.

A further object or a piece of tissue to be fixed to the bone tissueduring the implantation process may be placed between the tool and theimplant or between the implant and a lateral wall of the opening in thebone tissue. This also applies to the other embodiments according to thethird or first aspect of the invention.

FIG. 17 shows a further embodiment according to the third aspect of theinvention, wherein the force for expanding the implant during theimplantation acts as compression load on the tool. While the distal endportion 3.7 of the implant in embodiments like the ones according toFIGS. 15 and 16 must comprise a component with a growing cross-sectionfrom the proximal to the distal side, in embodiments like the oneaccording to FIG. 17, in which the tool is under compression load, adistal end portion with a growing cross-section from the distal to theproximal side is advantageous. In the illustrated example the distal endportion of the tool is designed like this.

For embodiments in which the force expanding the implant acts on thetool as compression load, the cross-sections of the shaft portion and ofthe distal end portion can be of equal size. The tool can be e.g.cylindrical, possibly tapering toward the distal side.

In the embodiment illustrated in FIG. 17 the implant is shaped like acup and rests upon the bottom of the opening in the bone tissue. Theimplant can also be tubular or of another shape comprising a recess.

In the embodiment of FIG. 17, the tool 3 can be shaped so that it can beremoved after implantation, for example if it narrows towards the distalside. As an alternative, the tool can be shaped so that it comprises aretaining structure (in the depicted embodiment formed by the shownshoulder) and itself serves as anchoring element after implantation.FIG. 17a depicts the tool 3 to comprise a threading 3.21 designed toco-operate with a threading of a further element 91, that may forexample be an abutment of a dental implant, a dental implant itself, ora prosthesis etc.

The tool of the embodiment according to FIG. 11 has, in addition to theeffect of compressing the implant, to some extent an expanding effect.The configuration according to FIG. 11 therefore corresponds to thefirst and the second aspect as well as to the third aspect of theinvention.

Implants according to the third aspect of the invention areadvantageously made entirely of the thermoplastic material.Non-thermoplastic components may be provided, e.g. at the base of acup-shaped implant, at the periphery of an area where no expansion isdesired, or as a reinforcing element designed and situated not toobstruct the expansion. In the case of a tube- or cup-shaped implantsuch reinforcements can e.g. be of an elongated shape and extend spreadout on the circumferential surface of the implant in axial direction.

In all embodiments according to the first and the third aspect of theinvention, the opening (if present) in the implant does not need to becentral. A corresponding asymmetrical configuration can be used in orderto specifically liquefy or plastify the thermoplastic material on oneimplant side earlier than on the opposite side, or it may be intendedthat the thermoplastic material only liquefies or plastifies on oneside.

Also in cases, where the tool is under compression force, acounter-element 31 can be applied. Such an element acts on the distalside of the implant and is e.g. held by a shaft extending centrallythrough the tool, as illustrated in FIG. 18, which shows an exampleaccording to the first aspect of the invention. In such cases, it is notnecessary for embodiments according to the first aspect of the inventionthat the tool 3 is moved when force 4 is coupled into it. Instead, thecounter-element 31 coupling the counterforce 51 into the implant can bemoved during the implantation procedure. Combined motions of the tooland the counter-element are also possible. It is further possible thatthe counter-element 31 is designed as a tool and therefore also couplesmechanical vibrations into the implant, i.e. the mechanical vibrationsare coupled into the implant from two sides.

In all embodiments designed according to the second aspect of theinvention the force 4 to be coupled into the implant acts a tensileforce on the tool 3 or (as in configurations according to FIG. 18) ifnecessary on the counter-element 31. This requires an appropriatecoupling means on the vibratory device, which does not only need to besuitable for tensile force but also for the transmission of mechanicalvibrations while under tensile force. Such coupling means are known tosomeone skilled in the art. They are often based on a form fit (screwjoints, snap fastenings, bayonet catches, etc.) or possibly a materialfit (glued, welded or soldered connections) or a friction fit (clampedconnections). Such generally known coupling means are not furtherdiscussed here. The principle of a form-fit coupling means is shown inFIG. 19. This coupling can be used as shown or in an alternative form.The vibratory device comprises an extension protruding into a clearanceat the proximal end of the tool 3 and widening towards its distal end sothat it can transmit a tensile force. For coupling the tool 3 to thevibratory device, these are moved perpendicular to the plane of FIG. 19relative to each other. Dovetails or similar modifications may beconsidered. In embodiments such as shown in FIG. 13 these or othercoupling means can also be used to transmit tensile forces from the tool3 to the implant 1.

In embodiments where the tool 3 remains in place after implantation, thetool often is provided with a distal portion with a larger crosssection, said distal portion being arranged distal of a main portion ofthe implant (c.f. FIG. 4, FIG. 20.). In embodiments where the necessaryforce is applied to the tool as a compressive force, this is often notan option, as the tool there is moved “forward”, i.e. towards a distalside during implantation. FIG. 20 illustrates an embodiment of such“forward” implantation, where the tool 3 may nevertheless remain in theplace of the implantation after implantation. To this end, the tool isprovided with retaining structures 3.13 that cause the tool to beretained by the implant 1 after implantation. In FIG. 20, also a thread3.12 of the tool is illustrated that may be used to fix some otherobject to the implant.

FIGS. 21a and 21b illustrate another embodiment of the second aspect ofthe invention that is especially suited for affixing the implant tocortical bone. The tool 3 is provided with reaming structures 3.14 witha larger external diameter than the shaft 3.4. The tool is first used todrill a hole into the cortical bone by means of the reaming structures.Thereafter, the tube shaped implant 1 is pushed on the shaft. Theexternal and internal diameters of the implant 1 are such that it canpass through the hole, but abuts the reaming structures 3.14. Forimplanting, the implant is pressed against the counter element 31 bypulling the tool 3, the implant being compressed between the tool andthe counter element. The liquefiable material liquefies in contact withthe cortical bone material, and since this bone material is very hardwith little porosity, it may ooze out on the distal side of thecorticalis, form a bulge, and thereby act in a blind rivet like manner.

Instead of the tool comprising the reaming structures, it may alsocomprise a distal enlargement by which the force may act on the tool,and the hole in the corticalis may then be drilled by an instrumentdifferent from the tool.

Referring to FIGS. 22a and 22b, 23a, 23b , and 24, further examples ofthe third aspect of the invention are described. The embodiments ofimplants 1 shown therein comprise an implant section (in both depictedembodiments the implants consist of said section) consisting of athermoplastic material, where during implantation a distal portion ofthe tool 3 protrudes into an interior of said section and duringimplantation spreads the implant section from an inside. This results inlateral forces onto the interfaces between the implant and the hardtissue or hard tissue replacement material surface, thereby improvinganchoring in lateral walls of the tissue/tissue replacement material.The depicted embodiments show two possibilities to spread the implant,by the tool, from the inside:

The tool 3 is driven into the implant during implantation, therebyenlarging an outer cross section (FIGS. 22a, 22b ). The tool in theshown embodiment comprises barb-like structures for the tool being keptfixedly in the implant after implantation.

The tool is not rotationally symmetric and is rotated duringimplantation, while rotation of the implant is inhibited (FIGS. 23, 23b, 24). In FIGS. 23a, 23b , the tool comprises a plurality of eccentrics3.11, whereas in FIG. 24 both the tool and the opening in the implantare translation symmetric but not rotational symmetric, and are, in theillustrated embodiment, hexagonal in cross section. The depictedimplants 1 comprise barb like protrusions 1.31 inhibiting rotation.

The methods and implants described in this text may be used for a broadvariety of surgical applications. For example, implants according to theinvention may be used in almost any applications where hitherto screwsor anchors were placed in bone; this includes the fixation of fracturesor distractions by pin like implants, the fixation of prostheses byexpanding stem like elements in the cancellous bone or in theintermedullary canal, an approach that could also be used to achievedistal and proximal locking of intermedullary nails, the fastening ofplates, membranes or meshes with the aid of pin like implants using thisembodiment, the fastening of ligaments or tendons by suture anchorsespecially in thinner bone structures, the fastening of webs etc. theexpansion principle is suitable to achieve anchoring in osseousmembranes, implants for cranial and maxillofacial surgery or forfixation in the shoulder blade, Sternum (closure of osteotomies) (U.S.application Ser. No. 11/694,249 being incorporated herein by referenceshows some examples with specially designed implants).

Some of the new applications of implants are described in this text.These applications described herein are mere examples of new uses theapproach according to the invention makes possible, the new applicationsbeing by no means restricted to the described examples.

FIGS. 25a and 25b show, in a generic way, how implants according to theinvention may be used in the place of a state of the art compression orlag screw used to press one hard tissue part against another hard tissuepart. The implant 1 comprises an implant portion (in the picturedembodiment being the distal implant portion) corresponding to the firstand/or second aspect of the invention; for example being configured asdepicted in FIG. 3a /FIG. 4. This distal implant portion is anchored ina first, distal bone fragment 21.1 by the method described referring toFIG. 4, the implant shaft 1.24 thereby serves as the counter element(FIG. 25a ). Thereafter, optionally a proximal portion of the tool 3 isremoved, and a proximal portion of the implant is at least partiallyplastified or liquefied to form an implant head and/or to interpenetratestructures of the surfacing bone material of a second, outer bonefragment 21.2 (FIG. 25b ) or standard counter-locking elements as formedheads, plates and meshes are used.

The implant shaft 1.24 in this embodiment may consist of thethermoplastic material liquefiable by mechanical oscillations, or it maycomprise material portions of non-liquefiable material.

In FIG. 26 an example of resurfacing of a joint by means of an implantand a method according to the invention is illustrated. The depictedbone 21 is a femur, of which the femoral head or a cup like structureacting as a resurfacing prosthesis replacing primarily the destroyedcartilage layer but sparing most of the underlying bone structure isreplaced. This is shown here for a femoral head resurfacing prostheses,comparable approaches can be used for almost all joints in the humanskeleton, being convex, concave, flat or of multicurvature geometry. Thetool 3 is fastened in a bore in the femur by means of the joint use ofthe methods according to the first and second aspect of the invention asillustrated in FIG. 11 (as an alternative, other embodiments of themethod according to the invention could be used, for example theembodiment depicted in FIG. 4, or the embodiment shown in FIG. 17aetc.). The shaft 3.4 of the tool 3 serves as anchor for fastening theresurfacing prosthetic element 102. Depending on the joint, severaltools 3 might be inserted to allow for a multipoint-anchoring of theelement 102.

Of course, various other embodiments of implants can be envisaged.

Implants, devices and implantation methods according to the illustratedor other embodiments of all aspects of the invention find their use invarious situations where a firm connection between the implant and thebone tissue is important. For anchoring implants in osteoporotic bonetissue and for other specific applications reference is made to allapplications as described in the publications WO 02/069 817, WO 2004/017857 and WO 2005/079 696, whose contents are incorporated herein byreference.

What is claimed is:
 1. A method of anchoring an implant in hard tissueor hard tissue replacement material, the method comprising the steps of:providing an opening in the hard tissue or hard tissue replacementmaterial; providing the implant, the implant being compressible in thedirection of a compression axis under local enlargement of a distancebetween a peripheral surface of the implant and the compression axis,wherein the implant comprises a coupling-in face not parallel to thecompression axis for the coupling-in of a compressing force andmechanical vibration, and wherein the implant further comprises athermoplastic material forming at least a part of the peripheral implantsurface in areas of the local distance enlargement, positioning theimplant in the opening such that the thermoplastic material of theimplant is in contact with the hard tissue or hard tissue replacementmaterial when the compressing force is coupled into the implant;coupling the compressing force and the mechanical vibrations via thecoupling-in face into the positioned implant, whereby the implant iscompressed and due to the distance enlargement at least locally pressedagainst lateral walls of the opening and the thermoplastic material, asa result of being pressed against the lateral walls, is at least partlyliquefied where in contact with the lateral walls and pressed intostructures of the hard tissue or hard tissue replacement material toform, after re-solidification, a form-fit connection with the lateralwalls.
 2. The method according to claim 1, wherein, on positioning theimplant in the opening, the compression axis is directed essentiallyparallel with an axis of the opening.
 3. The method according to claim1, wherein the implant comprises at least two implant components andwherein the implant components are moved relative to each other by theeffect of the compressing force by being shifted along shifting surfacesextending obliquely to the compression axis.
 4. The method according toclaim 3, wherein at least one implant component is spread by the effectof the compressing force.
 5. The method according to claim 4, whereintensions in the implant components generated by the deformation or thespreading or buckling respectively are reduced by the effect of themechanical vibrations.
 6. The method according to claim 3, wherein atleast a part of the implant components comprises a thermoplasticmaterial in the area of the shifting surfaces and wherein at least apart of the implant components are welded together by the mechanicalvibrations.
 7. The method according to claim 1, wherein the implantconsists of one piece and is deformed by the effect of the compressingforce.
 8. The method according to claim 7, wherein the compressing forcecauses the implant to spread or buckle.
 9. The method according to claim1, comprising the additional step of, prior to coupling the compressingforce into the implant, providing a spreading element and causing thespreading element to effect at least a part of the local enlarging of adistance between the peripheral surface of the implant and thecompression axis due to the effect of the compression force.
 10. Themethod according to claim 1, wherein the compressing force is exertedbetween a tool by which the mechanical vibrations are coupled into theimplant and a counter-element.
 11. The method according to claim 10,wherein the counter-element does not lead the hard tissue or hard tissuereplacement material.
 12. The method according to claim 10, wherein theimplant comprises at least two implant components and wherein theimplant components are moved relative to each other by the effect of thecompressing force by being shifted along shifting surfaces extendingobliquely to the compression axis.
 13. A method of anchoring an implantin an opening formed in hard tissue or hard tissue replacement material,said opening being defined by lateral walls of said hard tissue or hardtissue replacement material, the method comprising the steps of:providing the implant, the implant being compressible in the directionof a compression axis to locally enlarge a distance between a peripheralsurface of the implant and the compression axis, said peripheral surfaceof the implant comprising a solid thermoplastic material, wherein theimplant comprises a coupling-in face not parallel to the compressionaxis for the coupling-in of a compressing force and mechanicalvibration; positioning the implant in the opening such that the solidthermoplastic material is adjacent to the hard tissue or hard tissuereplacement material; coupling the compressing force and the mechanicalvibrations into the positioned implant via the coupling-in face so as tocompress the implant and thereby locally enlarge the distance betweenthe compression axis and the peripheral surface of the implant andthereby press the solid thermoplastic material on the implant peripheralsurface against the lateral walls of the hard tissue or hard tissuereplacement material defining the opening; continuing to couple thecompressing force and the mechanical vibrations into the implant andthereby liquefying the solid thermoplastic material being pressedagainst the lateral walls; pressing said liquefied thermoplasticmaterial into structures of the hard tissue or hard tissue replacementmaterial to form, after re-solidification, a form-fit connection withthe lateral walls, wherein the implant comprises at least two implantcomponents and wherein the implant components are moved relative to eachother by the effect of the compressing force by being shifted alongshifting surfaces extending obliquely to the compression axis.
 14. Themethod according to claim 13, wherein, on positioning the implant in theopening, the compression axis is directed essentially parallel with anaxis of the opening.
 15. The method according to claim 13, wherein atleast one implant component is spread by the effect of the compressingforce.
 16. The method according to claim 15, wherein tensions in theimplant components generated by the deformation or the spreading orbuckling respectively are reduced by the effect of the mechanicalvibrations.
 17. The method according to claim 13, wherein at least apart of the implant components comprises thermoplastic material in thearea of the shifting surfaces and wherein at least a part of the implantcomponents are welded together by the mechanical vibrations.
 18. Themethod according to claim 13, wherein the implant consists of one pieceand is deformed by the effect of the compressing force.
 19. The methodaccording to claim 18, wherein the compressing force causes the implantto spread or buckle.
 20. A method of anchoring an implant in an openingformed in hard tissue or hard tissue replacement material, said openingbeing defined by lateral walls of said hard tissue or hard tissuereplacement material, the method comprising the steps of: providing theimplant, the implant being compressible in the direction of acompression axis to locally enlarge a distance between a peripheralsurface of the implant and the compression axis, said peripheral surfaceof the implant comprising a solid thermoplastic material, wherein theimplant comprises a coupling-in face not parallel to the compressionaxis for the coupling-in of a compressing force and mechanicalvibration; positioning the implant in the opening such that the solidthermoplastic material is adjacent to the hard tissue or hard tissuereplacement material; coupling the compressing force and the mechanicalvibrations into the positioned implant via the coupling-in face so as tocompress the implant and thereby locally enlarge the distance betweenthe compression axis and the peripheral surface of the implant andthereby press the solid thermoplastic material on the implant peripheralsurface against the lateral walls of the hard tissue or hard tissuereplacement material defining the opening; continuing to couple thecompressing force and the mechanical vibrations into the implant andthereby liquefying the solid thermoplastic material being pressedagainst the lateral walls; pressing said liquefied thermoplasticmaterial into structures of the hard tissue or hard tissue replacementmaterial to form, after re-solidification, a form-fit connection withthe lateral walls, prior to coupling the compressing force into theimplant, providing a spreading element and causing the spreading elementto effect at least a part of the local enlarging of the distance betweenthe peripheral surface of the implant and the compression axis due tothe effect of the compression force.
 21. A method of anchoring animplant in an opening formed in hard tissue or hard tissue replacementmaterial, said opening being defined by lateral walls of said hardtissue or hard tissue replacement material, the method comprising thesteps of: providing the implant, the implant being compressible in thedirection of a compression axis to locally enlarge a distance between aperipheral surface of the implant and the compression axis, saidperipheral surface of the implant comprising a solid thermoplasticmaterial, wherein the implant comprises a coupling-in face not parallelto the compression axis for the coupling-in of a compressing force andmechanical vibration; positioning the implant in the opening such thatthe solid thermoplastic material is adjacent to the hard tissue or hardtissue replacement material; coupling the compressing force and themechanical vibrations into the positioned implant via the coupling-inface so as to compress the implant and thereby locally enlarge thedistance between the compression axis and the peripheral surface of theimplant and thereby press the solid thermoplastic material on theimplant peripheral surface against the lateral walls of the hard tissueor hard tissue replacement material defining the opening; continuing tocouple the compressing force and the mechanical vibrations into theimplant and thereby liquefying the solid thermoplastic material beingpressed against the lateral walls; pressing said liquefied thermoplasticmaterial into structures of the hard tissue or hard tissue replacementmaterial to form, after re-solidification, a form-fit connection withthe lateral walls, wherein the compressing force is exerted between atool by which the mechanical vibrations are coupled into the implant anda counter-element.
 22. The method according to claim 21, wherein theimplant comprises at least two implant components and wherein theimplant components are moved relative to each other by the effect of thecompressing force by being shifted along shifting surfaces extendingobliquely to the compression axis.